The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawings will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.
1. Field of Invention
This invention relates to a microporous inkjet receptor that provides excellent images with pigmented inks deposited thereon.
2. Background of Invention
Inkjet imaging techniques have become vastly popular in commercial and consumer applications. The ability to use a personal computer and desktop printer to print a color image on paper or other receptor media has extended from dye-based inks to pigment-based inks. The latter provide brilliant colors and more durable images because pigment particles are contained in a dispersion before being dispensed using a thermal inkjet print head, such as those commercially available from Hewlett Packard Corporation or LexMark Corporation in inkjet printers commercially available from Hewlett Packard Corporation, Encad Inc., Mimaki Corporation, and others.
Ink jet printers have been in general use for wide-format electronic printing for applications such as, engineering and architectural drawings. Because of the simplicity of operation, economy of ink jet printers, and improvements in ink technology the inkjet imaging process holds a superior growth potential promise for the printing industry to produce wide format, image on demand, presentation quality durable graphics.
The components of an ink jet system used for making graphics can be grouped into three major categories:
1 Computer, software, printer.
2 Ink.
3 Receptor sheet.
The computer, software, and printer will control the size, number and placement of the ink droplets and will transport the receptor film. The ink will contain the colorant or pigments which form the image and the receptor film provides the medium which accepts and holds the ink. The quality of the ink jet image is a function of the total system. However, the composition and interaction between the ink and receptor film is most important in an ink jet system.
Image quality is what the viewing public and paying customers will want and demand to see. Many other demands are also placed on the ink jet media/ink system from the print shop, such as rapid drying, humidity insensitivity, waterfastness and overall handleability. Also, exposure to the environment can place additional demands on the media and ink (depending on the application of the graphic).
Porous film is a natural choice to use as an ink jet receptive media because the capillary action of the porous film can wick the ink into the pores much faster than the absorption mechanism of film forming water soluble coatings. However, in the past, when a porous coating or film has been employed to achieve desired quick dry, optical density has suffered greatly because the colorant penetrates too deep into the porous network. This type of problem is magnified by printers that dispense high volumes of ink per drop because extra film thickness may be required to hold all the ink. When the pore size and pore volume of the membrane are opened to allow the pigments to penetrate, the pigments can be stratified in the membrane. Meaning, the black, cyan, magenta, and yellow will be predominately found at different depths depending on the order of application. Furthermore, lateral diffusion of the ink can also be a problem inherent in porous membranes used as receptive media. Hence, some of the first color(s) applied is/are optically trapped in the image by subsequent application of other pigmented ink When pigmented inks are jetted onto a porous film that has a pore size that is too small, color pigments will be filtered on the top of the membrane rendering high image density, but the pigments will easily smear and have the effect of never drying. Also, excess fluid from the ink can pool and run on the image before the water/glycol carrier is wicked away.
The chemical formulation of the pigmented inkjet ink has considerable complexity due to the requirement of continued dispersion of the pigment particles in the remainder of the ink.
The typical consumer medium for receiving dye-based inkjet inks has been paper or specially coated papers. However, with too much inkjet ink in a given area of the paper, one can see the over-saturation of the paper with the aqueous ink in which dye was dissolved.
As inkjet inks have become more commercially oriented and pigmented-based inks have become more prevalent, different media have been tried in an attempt to control the management of fluids in the ink. For example, copending, coassigned, U.S. patent application Ser. No. 08/614,986 (Steelman et al.), now abandoned, combines a hygroscopic layer to manage fluids in the ink with a hydrophilic layer thereon, upon which the ink can be deposited. Pigment particles remain with the hydrophilic layer while fluids pass through to the hygroscopic layer for rapid drying.
Ink receptive element containing absorptive polymers and polymer particles together with a binder has been disclosed in U.S. Pat. No. 5,084,340.
U.S. Pat. No. 4,781,985 discloses an inkjet transparency film comprising a substantially transparent resinous support containing a clear absorptive coating thereon.
U.S. Pat. No. 5,102,731 mentioned the use of a non-porous substrate and a coating layer formed thereon comprising a carboxyl group-containing ionomeric hydrophilic urethane resin and organic and/or inorganic fine particles.
U.S. Pat. No. 4,954,395 discloses a recording medium which comprises a porous ink-transporting layer and a non-porous ink-retaining layer.
German Patent No. 30 24 205 uses a pigment/binder mixture on the ink receiving paper. The purpose of the pigment is to add whiteness and porosity. A high pigment load leads the film to high porosity. This makes the paper smudge proof but this has a negative effect on optical density, because the dyes in the ink are drawn into the interior of the material.
Japanese Patent JP 61-041585 discloses a method for producing printing material using a ratio of PVA/PVP. The disadvantage is inadequate waterfastness and wet rub off properties.
Japanese Patent JP61-261089 discloses a transparent material with cationic conductive resin in addition to a mixture of PVA/PVP. The material is water fast and smudge proof but the wet rub off properties are poor.
U.S. Pat. No. 5,569,529 discloses a coating with PVP/PVA with water soluble compounds containing aldehyde groups. They also added quaternary ammonium compounds such as polydiallyldimethylammonium chloride. Plus on the backside of the paper they coat on hydropilic colloidal binders such as starch, PVA, or oxidized potato starch. Some color density is lost when submerged in water but after the initial loss it is resistant to further color loss by a weak rubbing test.
European Patent Publication EP 0 716 931 A1 discloses a system using a dye capable of co-ordinate bonding with a metal ion in two or more positions. Again binder resins are used with inorganic pigments in the paper or film. The metal ion was preferred to be jetted on before imaging and additional heating is necessary to complete the reaction. This system was not claiming to be water fast; the focus was long term storage without fading from heat or light.
U.S. Pat. No. 4,419,388 discloses a waterproofing system where after imaging one sprays on a compound containing a mono-valent metal atom or ammonium group with a tri-valent metal atom. An example of these compounds claimed are KAl(SO4)2.12 H2O. Claim 8 discloses aluminum sulfate can be applied to the paper before imaging, but the mono-valent component then has to be in the ink.
U.S. Pat. No. 5,537,137 discloses a system to achieve waterfastness by curing with heat or UV light. In the body of the patent, examples of their coatings contained Ca++ from CaCl2. This was added to provide reactive species for the acid groups on the dispersed polymer. The coating remains water soluble until UV or heat curing after imaging.
U.S. Pat. No. 4,649,064 uses multivalent metal salts in a gelatin coating to cross-link inks that contain polyesteramide with sulfonate functional groups. The ink receiving layer is crosslinked with bis(vinylsulfonylmethyl)ether. Careful selection of materials is required because the metal salts are capable of cross-linking the gelatin coating before the ink is applied.
U.S. Pat. No. 4,732,786 also uses an insolubilized hydrophilic polymer (gelatin) with polyvalent cations from metallic salts and claims advantages with their methods because they can make the coating with a low pigment/binder ratio.
U.S. Pat. No. 5,429,860 discloses an ink/receptor system that may contain multivalent cations. This system is UV activated after imaging to cross-link the materials.
Hence, the current special ink jet media employ vehicle absorptive components, and sometimes optional additives to bind the inks to the media. As a consequence current media are inherently moisture sensitive and can be fragile to handling and subject to finger smearing. Moreover, the vehicle absorptive components usually consist of water soluble (or swelling) polymers which result in slower printing speeds and dry times.
Pigmented ink delivery systems have also dealt with pigment management systems, wherein the resting location of the pigment particles are managed to provide the best possible image graphic. For example, copending, coassigned, U.S. Pat. No. 5,747,148 (Warner et al.) discloses a pigment management system in which a suitable supporting layer (including in a listing a microporous layer) has a two layer fluid management system: a protective penetrant layer and a receptor layer, both layers containing filler particles to provide two different types of protrusions from the uppermost protective penetrant layer. Electron microphotographs in that application show how the pigment particles of the ink encounter smooth protrusions that provide a suitable topography for pigment particle xe2x80x9cnestingxe2x80x9d and rocky protrusions that assist in media handling and the like.
Other ink receptors have been disclosed, including U.S. Pat. Nos. 5,342,688 (Kitchin); 5,389,723 and U.S. Pat. No. 4,935,307 (both Iqbal et al.); U.S. Pat. No. 5,208,092 (Iqbal) U.S. Pat. No. 5,302,437 (Idei et al); U.S. Pat. No. 5,206,071 (Atherton et al.); and EPO Patent Publication 0 484 016 A1.
While each of the fluid management systems and each of the pigment management systems of the above prior efforts are suitable for the uses intended, none of these prior disclosures recognizes the need for an inkjet receptor that has both a pigment management system for flocculating or agglomerating incoming ink and a fluid management system for efficiently dispensing with the carrier fluids within a porous substrate.
What is needed is new technology to permit the use of porous membranes that will achieve high quality imaged graphics with quick drying without water soluble/swellable polymers, or additional processing, or the current porous film drawbacks discussed above. Another need in the art is the ability to tailor a microporous medium based on the ink used and the printer configurations.
Furthermore, no two inks are exactly alike in formulation and no clear printer configuration standard has emerged. This variability in the marketplace requires adjustment in the remaining element of the ink jet printing system that is in control of the user, the receptor medium employed.
While Warner et al. above discloses the use of a microporous medium as the supporting layer, Warner et al. provide their fluid management system using two coating layers. The art needs a microporous receptor that does not require coating layers on a major surface of the receptor yet provides both pigment and fluid management systems.
One aspect of the present invention is an inkjet receptor medium, comprising a porous substrate having a fluid management system and having a pigment management system in contact with surfaces of pores of the substrate therein.
Another aspect of the invention is an inkjet receptor comprising a microporous membrane impregnated with a multivalent metal salt together with a surfactant or combination of surfactants chosen for the ink and membrane being employed.
Another aspect of the present invention is an inkjet receptor comprising a microporous membrane impregnated with a microporous fluorinated silica agglomerate together with a binder and a surfactant or a combination of surfactants for the ink and membrane being employed.
Another aspect of the present invention is an inkjet receptor comprising a microporous membrane impregnated with a microporous fluorinated silica agglomerate together with a binder and a surfactant or combination of surfactants wherein the said surfactants are selected from the group of hydrocarbon-based anionic surfactants, silicon-based non-ionic surfactants or fluorocarbon-based non-ionic based surfactants or a combination thereof.
The novel receptors, when imaged in an inkjet printer, provide very high density and very high quality images which are tack-free and instantaneously dry to touch.
Another aspect of the present invention is an impregnation for a porous media/ink set, making possible high speed production of high quality graphic images for current and future ink jet technologies. The imbibed porous substrate provides improved durability, waterfastness, smear resistance, effective quick dry times, and long term durability using porous film without absorptive polymeric binders, or additional process such as UV exposure or heating. Accordingly, the invention provides a media/ink set comprising: a microporous membrane that bears a surface modifier impregnated therein, containing wetting surfactant(s) and a water soluble multivalent metal salt(s), and an ink that contains pigment colorants.
In a preferred embodiment, the ink colorant is a pigment dispersion having a dispersant that binds to the pigment that will destabilize, flocculate, agglomerate, or coagulate the pigments on contact with the media component. Depositing each of colors at or just below the surface of the membrane allowing the carrier fluid to wick into the membrane where the fluid management system can take over while providing a sheltered location for the pigments as managed by the colorant management system.
Also preferred for the receptive media is a Thermally Induced Phase Separated (T.I.P.S.) microporous membrane disclosed in U.S. Pat. No. 4,539,256 (Shipman) and available from 3M. For optimization, the pore size and pore volume of the porous film can be adjusted for the model or make of the ink jet printer to correctly hold the volume of ink dispensed by the printer ensuring the highest possible image quality. The coating on the preferred media/ink set has special utility in the demanding ink jet printing applications found in commercial printing.
A feature of the present invention is the ability to xe2x80x9cfine tunexe2x80x9d the properties of receptors of the present invention to deal with the variables of inkjet ink delivery, including without limitation: drop volume, porosity of media, and capacity of media to receive ink.
Another feature of the present invention is that it allows the use of complex porosity in a porous material that provides both a tortuous path for fluid management and a tortuous path that ensnares the pigment initially and continually during ink delivery. A variety of presently commercially microporous media that have tortuous paths become useful when completed according the methods of the present invention which is a major limitation of the teachings of U.S. Pat. No. 5,374,475 (Watchli et al).
Another feature of the present invention is the ability to use the present invention for very rapid printing of brilliant, pigmented inkjet inks that dry rapidly as well.
Another feature is satisfaction of many goals of inkjet printing: is competitive in cost; works with pigmented inks; has high resolution; has high color density; has a wide color gamut; is waterfast; is smudge resistant; uses capillary action of the porous membrane for rapid fluid absorption (effective quick dry); does not show banding or coalescence; doesn""t show finger prints when handled before or after printing; is a brighter white that does not yellow in time; is stable during temperature and humidity swings; is very outdoor durable with or without an overlaminate; has long shelf life; and is superior when backlighting is used.
An advantage of the present invention is ease of manufacture of microporous receptors without topcoats.
Another advantage of the present invention is the images look excellent for reflective or backlit viewing without heat collapsing the porous substrate as is necessary according to U.S. Pat. No. 5,374,475 (Walchli et al.)
Another advantage of the present invention is very fast-drying of the impregnated salt or microporous silica/surfactant system during coating. The process helps save significant amounts of energy.
Optional additives such as stabilizers, ultraviolet light absorbers, anti-oxidants, mold inhibitors, dye mordants, binders, or polymers can be introduced into the receptors of the present invention so long as they do not interfere with the pigment or fluid management systems.
Optional additional layers can reside on a major surface designated for imaging, such as overlarninates and clear coatings that protect the image graphic. Alternatively, optional additional layers can reside on a major surface opposing the imaging surface, such as stronger layers for laminate construction or adhesive layers for adhesion of the image graphic to an installation surface, either permanently or temporarily. A release liner can be used to protect the adhesive layer during imaging and storage.
Other features and advantages will become identified in discussing embodiments of the invention, using the following drawings.